Organic light emitting diode has gradually become the mainstream for displaying and also can be used in various applications. Generally, the conventional pixel driving circuit of organic light emitting diode is designed with two transistors and one capacitor, which are for controlling brightness of the organic light emitting diode.
However, because the manufacturing variation and the aging degradation of the light emitting diode, the current flowing through the light emitting diode may be unstable and consequentially the associated display panel may have brightness non-uniformity issue. That is, because these pixel driving circuits are electrically coupled to a voltage source through metal wires having impedances, the IR-drop may occur when the light emitting diodes are being driven by the voltage source to illuminate light. Thus, the pixel driving circuits may have different pixel currents and consequentially the light emitting diodes may have different brightness. As a result, the non-uniformity issue occurs.